Here then arises a new species of probability to correct and regulate the first, and fix its just standard and proportion.

As demonstration is subject to the controul of probability, so is probability liable to a new correction by a reflex act of the mind, wherein the nature of our understanding, and our reasoning from the first probability become our objects.
Having thus found in every probability, beside the original uncertainty inherent in the subject, a new uncertainty derived from the weakness of that faculty, which judges, and having adjusted these two together, we are obliged by our reason to add a new doubt derived from the possibility of error in the estimation we make of the truth and fidelity of our faculties.

This is a doubt, which immediately occurs to us, and of which, if we would closely pursue our reason, we cannot avoid giving a decision.

But this decision, though it should be favourable to our preceding judgment, being founded only on probability, must weaken still further our first evidence, and must itself be weakened by a fourth doubt of the same kind, and so on in infinitum: till at last there remain nothing of the original probability, however great we may suppose it to have been, and however small the diminution by every new uncertainty.

No finite object can subsist under a decrease repeated IN INFINITUM; and even the vastest quantity, which can enter into human imagination, must in this manner be reduced to nothing.